This invention relates to a position sensing method and apparatus and particularly to a sensor assembly for sensing the angular position of a rotatable body.
It is desirable in many applications to sense the angular position of a rotatable body. For example, it is desirable in a motor vehicle to sense the angular position of the steering column and generate a control signal representative of the angular position of the steering column. This control signal may be used, for example, to control a steer-by-wire steering system, to vary the setting of an active suspension system in response to turning movement of the vehicle, or to control a four-wheel steering system.
The sensors employed to sense the angular position of a steering column are typically calibrated prior to installation on the steering column and it is imperative that the calibration zero position be maintained between the time that the sensor is calibrated and the time that the sensor is assembled onto the steering column. It is also imperative that, upon installation of the sensor on the steering column, the operative sensor member be free to rotate with the steering column whereby to generate a position signal indicative of the angular position of the steering column.
In one prior art design, these dual requirements have been satisfied by the use of an anti-rotation pin which lockingly interconnects the sensor operative member to the sensor housing to maintain the zero calibration position and which is removed following installation of the sensor on the steering column to allow the sensor operative member to freely rotate with the steering column. Whereas this pin design satisfies both requirements, the provision of the pin complicates the sensor design and increases the assembly time. The pin design also introduces the possibility that the installer may forget to remove the pin following installation of the sensor on the steering column.
This invention relates to an improved position sensor for use with a rotatable body.
More specifically this invention relates to a position sensor having provision to maintain the zero calibration of the sensor prior to installation on the rotatable body and to automatically release the operative element of the sensor for rotation with the rotatable body in response to installation of the sensor on the rotatable body.
One aspect of the invention relates to a method of mounting a sensor assembly on the rotatable body following calibration of the rotatable element of the sensor assembly. According to the invention methodology, the rotatable element is calibrated; the rotatable element is lockingly engaged relative to the sensor housing to maintain the rotatable element in the calibrated position; and, with the rotatable element in the calibrated position, the sensor assembly is mounted on the rotatable body while simultaneously keying the rotatable element to the rotatable body and releasing the rotatable element from locking engagement with the sensor housing. This methodology maintains the zero calibration of the sensor prior to installation on the rotatable body and automatically releases the rotatable element of the sensor for turning movement with the rotatable body in response to mounting of the sensor on a rotatable body.
According to a further aspect of the invention methodology, the sensor assembly includes a connector member connected to the rotatable element and including a key structure for keying the connector member and rotatable element to the rotatable body and an anti-rotation structure for lockingly engaging the connector member to the sensor housing; the anti-rotation structure functions prior to the mounting step to maintain the calibrated position of the rotatable element; and, during the mounting step, the key structure functions to key the connector member and rotatable element to the rotatable body and the rotatable body is operative to move the anti-rotation structure out of locking engagement with a sensor housing. This methodology provides a ready and effective mechanism for maintaining zero calibration while automatically releasing the rotatable element of the sensor for rotation with the rotatable body in response to installation of the sensor on the rotatable body.
According to further aspect of the invention methodology, the connector member comprises a ring member having an annular main body portion; the key structure comprises a key finger projecting from the main body portion and sized for coaction with a keyway on the rotatable body; and the anti-rotation structure comprises an anti-rotation finger projecting from the main body portion at a location spaced circumferentially from the key finger and sized for receipt in a notch in the sensor housing. This specific connector member construction provides a ready and effective means of carrying out the invention methodology.
According to a further feature of the invention methodology, the anti-rotation finger includes a locking portion for engagement with the notch in the sensor housing and a release portion; and the release portion is operative during mounting of the sensor assembly on the rotatable body to move the locking portion out of engagement with the sensor housing notch in response to engagement of the release portion by the rotatable body. This specific connector member construction facilitates the step of releasing the rotatable element from locking engagement with the sensor housing in response to mounting of the sensor assembly on the rotatable body.
According to a further feature of the invention methodology, the rotatable element of the sensor comprises a ring gear having circumferentially spaced teeth on its external periphery and circumferentially spaced notches on its internal periphery; and the connector member further includes a plurality of circumferentially spaced coupling fingers projecting from the main body portion for respective receipt in the notches in the internal periphery of the ring gear. This arrangement provides a ready and effective means of coupling the connector member to the ring member to facilitate carrying out the invention methodology.
In the preferred embodiment of the invention the rotatable body comprises the steering column of a motor vehicle and the sensor assembly is operative to sense the angular position of the steering column and generate a control signal representative of the angular position of the steering column.
With respect to the apparatus aspect of the invention, the sensor assembly is of a type including a sensor housing, a rotatable element mounted in the housing, and means operative to sense the angular position of the rotatable element and generate a control signal representative of the angular position of the rotatable element.
According to the invention, the sensor assembly further includes a connector member for selectively interconnecting the rotatable body, the sensor housing, and the rotatable element, and the connector member includes a coupling structure for coupling the connector member to the rotatable element, a key structure for keying the connector member to the rotatable body in response to mounting of the sensor assembly on the rotatable body, an anti-rotation structure for lockingly engaging the connector member to the sensor housing to preclude rotation of the connector member and rotatable element relative to the sensor housing, and a release structure operative in response to mounting of the sensor assembly on the rotatable body to release the anti-rotation structure from locking engagement with the sensor housing and allow rotation of the rotatable element with the rotatable body. The recited connector member will be seen to provide a convenient means of maintaining the initial zero calibration of the sensor prior to installation on the rotatable body and to further provide automatic means to release the anti-rotation structure from locking engagement with the sensor housing in response to mounting of the sensor on the rotatable body.
According to further apparatus feature of the invention, the connector member comprises a ring member adapted to be positioned in surrounding relation to the rotatable body; the ring member includes an annular main body portion; the key structure comprises a key finger projecting from the main body portion for coaction with a keyway on the rotatable body; the anti-rotation structure comprises an anti-rotation finger projecting from the main body portion at a location spaced circumferentially from the key finger and coacting with a notch in the sensor housing; and the release structure comprises a release portion of the anti-rotation finger positioned in the path of the rotatable body as the sensor assembly is mounted on the rotatable body and operative in response to engagement with the rotatable body to move the anti-rotation finger out of the notch of the sensor assembly. The specific connector member construction facilitates the selective coaction between the connector member, the sensor housing, the rotatable element, and the rotatable body.
According to a further apparatus aspect of the invention, a pivot point is defined at the juncture of the anti-rotation finger and the main body portion and the point of engagement between the release portion of the anti-rotation finger and the rotatable body is spaced inwardly from the pivot point so that the anti-rotation finger is pivoted about the pivot point in response to engagement by the rotatable body. This specific pivotal arrangement provides a ready and effective means of unlocking the rotatable element of the sensor from the sensor housing as the sensor is mounted on the rotatable body.
According to a further apparatus aspect of the invention, the finger comprises a compound finger including a first finger portion extending inwardly from the main body portion and a second finger portion doubled over with respect to the first finger portion so as to extend outwardly to define a free end adapted to coact with the notch in the sensor housing. This specific finger construction provides both a locking and a release function in a single finger configuration.
According to a further apparatus aspect of the invention, the first portion of the compound finger extends downwardly and inwardly and the second portion extends upwardly and outwardly and has the length extending a length of the first portion so as to position the free end thereof above the main body portion to facilitate engagement with the sensor housing notch.
According to a further apparatus aspect of the invention, the coupling structure comprises a plurality of circumferentially spaced coupling fingers projecting from the main body portion for engagement with the rotatable element and the coupling fingers are further operative to center the sensor assembly with respect to the rotatable body as the sensor assembly is mounted on the rotatable body. The coupling fingers will be seen to enable the connector member to perform the dual functions of coupling the connector member and the rotatable element and centering the sensor assembly on the rotatable body as the sensor assembly is mounted on the rotatable body.